Fabric products, for example, sanitary products such as towels and bedclothes, and garments (hereinafter, in the present specification, also simply referred to as “fabric products”) provide a comfortable sense of use and wear sensation when the products are kept clean. Furthermore, fabric products such as sanitary products and garments are materials that are put on human bodies, and towels, bedclothes and the like are used by being brought into direct contact with human bodies. Therefore, it is important even from the viewpoint of hygiene to keep these materials clean. Along the enhanced recent social requirements for hygiene, the public interest in keeping fabric products such as sanitary products and garments clean has increased.
In recent years, as consumers build up more interest in the living environment, it is desired more than ever to remove any unpleasant odors (in the present specification, also referred to as “foul malodor”) of personal belongings. The odors that cling to fabric products, for example, sanitary products such as towels and bedclothes, and garments, include external factors such as cigarettes, as well as internal factors that re originated from human body, which are produced by repeated use of fabric products.
Fabric products that are brought into direct contact with human skin, including underclothes, towels, handkerchiefs and the like, or fabric products that have a potential to absorb or attach sweat containing sebum, comeous substances and the like, may produce a wet-and-dirty dustcloth-malodor-like characteristic malodor in a case where after laundry, laundered fabric products are left untouched in a damp place such as the inside of a laundering machine tub for a long time, in the case of having been dried indoors, in the case of having gotten wet with rain or sweat, or in the case of insufficiently dried fabric products. This malodor is generally called a damp-dry malodor, and this odor can be mostly eliminated by sufficiently drying the fabric products. However, even for fabric products which have been sufficiently dried and from which no damp-dry malodor is sensed, when the fabric products become damp due to sweat, rain or the like, the damp-dry malodor may be produced. If fabric products once produce this damp-dry malodor, the damp-dry malodor can be temporarily eliminated by sufficiently drying the fabric products after laundry, but the wet-and-dirty dustcloth-like damp-dry malodor is likely to recur at the time of use. Such a damp-dry malodor that is prone to recur may be produced not only in a case where fabric products are dried indoors, but also in a case where a dryer or a washing machine having a low temperature drying function is used, and even in the case of fabric products that have been dried outdoors, if the fabric products become damp.
A feature of the recurrent damp-dry malodor lies in that the malodor is not produced, or mostly reduced, if a fabric product has been laundered and sufficiently dried. However, the fabric product produces the malodor only by becoming damp. The recurrent damp-dry malodor is likely to be produced when fabric products are stored in a wardrobe or the like for a long time. However, fabric products such as underclothes, handkerchiefs or towels, which are frequently brought into contact with human skin and are used with a high use frequency and a short period of the wash-use cycle, are in many cases such that once this damp-dry malodor is produced, the malodor comes to recur during use.
Furthermore, as the number of times of laundering increases, the intensity of malodor of the damp-dry malodor tends to increase. In order to inhibit this damp-dry malodor, it is important to treat fabric products so as not to produce such damp-dry malodor-causing substances. As a method for that purpose, there is a demand for an agent which inhibits the damp-dry malodor. Also, there is a demand for the development of a method of screening a damp-dry malodor inhibitor and a method of evaluating a damp-dry malodor inhibitor.
It has been hitherto reported that the damp-dry malodor is a complex odor composed of the “mold-like malodor” of medium-chain aldehydes, medium-chain alcohols, ketones and the like, the “sour malodor” of short-chain fatty acids, medium-chain fatty acids and the like, the “fishy malodor” of nitrogen compounds, and sulfur compounds, and medium-chain fatty acids in particular have a high degree of contribution (see Non-Patent Literature 1). Furthermore, Non-Patent Literature 1 describes that a major component of the damp-dry malodor is speculated to be “a mixture of unsaturated fatty acids having a branched structure with 7 to 9 carbon atoms,” and these are also contained in the foul odor of human sweat or the like. As indicator substances for the damp-dry malodor, various kinds of fatty acids including 4-methyl-3-hexenoic acid have been hitherto suggested (see Patent Literature 1). The 4-methyl-3-hexenoic acid is naturally known as a component of citrons (see Non-Patent Literature 2), and it is also known that the 4-methyl-3-hexenoic acid is produced from terpenes by microorganisms (see Patent Literature 2). However, these literatures do not describe or suggest the mechanism of the production of the damp-dry malodor. Also, these literatures do not disclose the relation between various kinds of fatty acids including the 4-methyl-3-hexenoic acid and the recurrence of the damp-dry malodor. Furthermore, there is no instance of devising a method of screening a damp-dry malodor inhibitor and a method of evaluating a damp-dry malodor inhibitor based on such a mechanism.